1. Field of the Invention:
The present invention relates to an integral composite structure and method for forming same which includes a preselected pattern of electrically conductive pathways on preformed plastic parts thereby eliminating the need for separate electrical wiring, and, more particularly, to an integral composite structure and method for forming same having predetermined electrically conductive networks on a non-conductive, support structure, either planar or non-planar, which is formed by the combination of a relatively non-conductive slurry of electrically conductive materials having a carrier which includes a volatile fluid and an elastomeric substance in which particles of an electrically conductive material are suspended, the carrier being chemically reactive with the material forming the relatively non-conductive support structure so that following the combination of the slurry with the support structure the carrier reacts chemically with the support structure to create a bond therebetween and upon the deposition of a slurry of polymer-based materials which upon solidification forms an electrically conductive solid coating.
2. Description of the Prior Art:
Polymer thick conductors, often referred to as conductive "inks", for high-speed printing of flexible, electrically conductive patterns onto various types of non-conductive base surfaces, are known to exist in the prior art. Such inks typically are formed by combining silver metal particles of the desire mesh size, frequently 200 mesh, or 0.0021 inch diameter, mixed with a polymer/elastomeric carrier. Upon curing, the dried ink forms an excellent electrical conductor. Such are used in the formation of membranes for computer keyboards, and for deposition onto cloth, or paper, products.
There are various methods used for application of such conductive inks to non-conductive base surfaces. Such methods found in the prior art include screen printing, letterpress, Flexographic and Offset, as well as plating, painting, or electroplaining techniques. All of these methods share the problems encountered with perhaps the most frequently used technique is the use of the well-known screen printing process identified as "silk screen" printing. While such prior art techniques for applying the polymer conductive inks to a base surface are used, the silk screen method is not without its difficulties.
One problem which has known to plague the use of the silk screen method is that the very nature of the silk screen process is inherently wasteful of the relatively expensive polymer conductive ink material. In order to apply such conductive inks in a pattern established by the silk screen, the silk screen must be saturated with the conductive ink. The conductive ink held by the silk screen is then forced into the silk screen mesh typically by the manual manipulation of a squeegee passed thereinover and is deposited onto the non-conductive base disposed on the opposite side of the silk screen material upon removal of screen contact with the part. In this process, only a small fraction of the conductive ink held by the silk screen itself will be effectively transferred to the non-conductive base material; the balance remaining in the silk screen material is, for all intents and purposes, lost and wasted. Of course, perhaps several another non-conductive base material items can be inserted thereinunder before the conductive inks solidify. Nevertheless, when production ceases at some point in time, the ink which remains captured in the silk screen will solidify and be effectively lost and no longer will be usable for the purpose intended. At $30.00 dollars, or so, per ounce this can become a very expensive proposition rather quickly.
Another significant problem encountered with the use of the silk screen process involves the deposition of such electrically conductive inks on relatively large areas of the silk screen itself as compared to the designated ink transfer area of the silk screen and exposing the unused portion to air and thus drying continuously. In essence, there is a significantly substantial waste factor associated with the silk screen process.
Further, silk screen cannot easily be applied, or used, for non-planar applications.
In a great many applications, electrically conductive wires formed of drawn copper or aluminum metal and coated with plastic, rubber or other non-electrically conductive materials, are used to conduct electricity from the electrical power source to the desired point of use. However, the use of such wiring is costly in a great number of applications because of its manual labor-intensive mode of installation in a given application. In other applications, it simply cannot be used because of the relatively large size of the solid metal wiring, whether insulated or uninsulated. In short, the use of such wiring is virtually a "custom" installation and presents a very high cost means of conducting electrical energy from its source to point of use.
In a number of other electrical applications, such electrically conductive paths are created using printed circuit boards, multi-layer printed circuit boards, and the like, are created by etching away portions of an electrically conductive metallic substance clad to a non-electrically conductive planar base by a combination of masking and a liquid chemical suitable for removing the electrically conductive metallic substance from the non-conducting base material.
Sometimes an electrically conductive material is sprayed onto a non-electrically conductive base, by electrical or gas plasma methods to form a particular pattern of electrically conductive pathways on the base material.
All of the prior art methods while usable, are frequently undesirable for one or more reasons, such as being too costly to apply, excessive labor intensive installation, produces toxic or non-toxic waste during and after its application or formation, or requires costly machinery to effectuate their use, application and formation.
An additional problem which is frequently encountered in the use of prior art methods enumerated herein is the extreme difficulty in producing acceptable quantities of relatively large non-planar composite structures of the type characterized herein.
Use of the present method to form such electrically conductive pathways on a preformed support structure largely overcomes the objections of prior art methods and devices in the creation of such electrically conductive pathways in not only planar structures but non-planar structures as well.
The present method represents a new and novel advance in the state of the art of installing, supporting and forming partially insulating electrically conductive pathways as an integral part of the modular device to be electrically powered.
In utilizing such a new and novel approach to the integration of electrically conductive pathways on a non-electrically conductive base expense, weight, and space savings, as well as a significant reduction in labor-intensive activities can be expected.
Another significant and important object of the instant invention is to provide a means for producing the composite article of manufacture of the type characterized herein involving non-planar support structures.
Other features, and important characteristics of the instant invention will be further realized as this new and novel method is further detailed hereinafterwards.